David isn't with Thomas in 1891. Here's Thomas in 1881 - note the elder daughter
address Tavernypiod, Llandilo Talybont
Thomas Mathews 56 - widow,, Coal Proprietor Employing 5 Men
Ann Mathews 19 - daughter b Llandilo Talybont
Jennet Mathews 13 - daughter b Lougher
Rachel Stradling 50 - boarder
Wm. Stradling 19 - boarder
RG11, 5350, 80, 7